I'm buying my first set of tires (606/908)for the 990, and the website from which I purchase tires warns that UHD (or even HD) tubes should not be used on the street. While I often ride the road between dirt destinations, I've been using UHD tubes on the 525 for years without event.

Is there some reason about which I'm ignorant that the UHD tubes are a hazard on the big bike, on the street? I'm sure "heat" is one possible explanation.

I recall hearing that there were heat buildup issues at the speeds the big bikes are capable of, probably a fear of lawsuits or something if one of them fails at some seriously high speeds. I guess tubes move around a bit inside of a tire carcass, and the heavier tubes probably build more heat.

I don't really know what the supposed issues with UHD tubes are but I do know that I run (and have run for the past 7,000 miles or so) Michelin UHD tubes in both my tires. I've also run the bike at some serious speeds (80+ offroad , and well over 100 on tarmac - closed course of course ) with no issues so far. The high speed riding is irregular and of course, something bad could happen one day...but so far no issues.

I do recall one time, on an XRL650 that was all hotrod, and would cruise at close to 100, that when I pulled a tire off, there was all this rubber dust in there, and a mechanic/tire guy told me that was the tube moving around at speed, grinding itself apart, maybe that is what they are trying to avoid.

I ran UHD for a while after initial purchase of the bike, having run HD and UHD on dirt bikes for years.

There were no problems with the tubes failing, other than one time with lower pressure I spun the wheel in the tire and ripped the stem out. This wasn't the fault of the tube. I probably put ten or fifteen thousand miles on those tubes through several tires, primarily street miles with many gravel roads and a few trails.

When it came time to replace the UHD tubes I considered how I had a number of puncture flats with them over the course of time. Avoiding punctures and pinches was the primary reason for going with UHD in the first place. It didn't seem to be working out for me.

I weighed the added cost of UHD against running a regular tube and RideOn sealant, and decided to go with the sealant instead of UHD. It seems like I've had fewer flats running a regular tube with sealant. Certainly no more flats than with UHD. The additional costs and issues with UHD, to me, provide marginal, if any, advantage over regular or HD tubes on our big bikes.

Other advantages to running regular tubes with sealant include:

Less gyroscopic mass in the wheels make cornering transitions easier.

No worries about overheating tube or tire.

Less heat may increase tire life.

Tire/wheel balance is less problematic.

Carrying spare tubes is less bulky.

Fewer flats and punctures are sealed quickly.

Lower replacement costs.

Greater availability of regular or HD tube at dealers.

For me the promise of higher reliability with UHD wasn't worth the extra expense and drawbacks associated with these tubes. I think that on a full on light weight dirt bike, like those used by enduro and hare scrambles racers, the UHD will offer some protection against pinch flats when running low pressures. On our gargantuan beasts it is probably better just to run a little higher tire pressure, lighter tubes, and sealant.

For me it is an ongoing study.

YMMV

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Running the 908 rear with UHDs would get VERY hot on tarmac.
I've had it melt two patches on a multi-flat ride where I was forced to use patches.
I'd get 50-100 miles and patch would leak & peel off from the heat.
Tire was barely touchable
I just run Metzler or Bridgstone standard tubes after that loooong weekend.

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Running the 908 rear with UHDs would get VERY hot on tarmac.
I've had it melt two patches on a multi-flat ride where I was forced to use patches.
I'd get 50-100 miles and patch would leak & peel off from the heat.
Tire was barely touchable
I just run Metzler or Bridgstone standard tubes after that loooong weekend.

I had a similar problem with patches failing. For me it turned out it wasn't heat, but old patches. It seems they have a shelf life of about a year, after which they won't chemically bond properly.

After losing three consecutive patches I did some research and learned that fresh patches work best and become less effective over time. I bought new patches and cement and it worked the first time and has been holding for months now.

If your patches are over a year or two past manufacture, including time in distribution, sitting on the shelf at the store, and in your repair kit, it is probably time to replace them.

Could be that riding on low air pressure leaking from a poor bond led to the heat you noticed.

Something to consider.

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Yeah, sorta what I thought. I've been exchanging email with the tire folks who've assured me that the 990/606/908 combination is no problem for the UHD tubes despite the earlier warnings.

But I do question the UHD paradigm. I've run them for years on the 525, but the big bike is different. The 606 run on the smaller bike carries a load of something like 275 lbs at fairly low sustained speeds. The same 606 on the big bike will carry closer to 375 at much higher sustained.

Further, the small bike will be lower psi- I usually run about 10-13. I think if I run that low pressure on the big bike (off road), I'll be buying a new front rim pretty quick.

Never saw a need for UHD tubes. If a thorn or a nail goes through the tire carcass, it's going to go through the tube. Buy two name brand standard weight tubes for the price of one UHD and put the other in your panniers.

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